1-229432868-C-T

Position:

• chr1-229432868-C-T

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PM2 PM5 PP2 PP3_Moderate PP5_Very_Strong

The NM_001100.4(ACTA1):​c.142G>A​(p.Gly48Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G48A) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: ACTA1 NM_001100.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.91

Genes affected

ACTA1 (HGNC:129): (actin alpha 1, skeletal muscle) The product encoded by this gene belongs to the actin family of proteins, which are highly conserved proteins that play a role in cell motility, structure and integrity. Alpha, beta and gamma actin isoforms have been identified, with alpha actins being a major constituent of the contractile apparatus, while beta and gamma actins are involved in the regulation of cell motility. This actin is an alpha actin that is found in skeletal muscle. Mutations in this gene cause a variety of myopathies, including nemaline myopathy, congenital myopathy with excess of thin myofilaments, congenital myopathy with cores, and congenital myopathy with fiber-type disproportion, diseases that lead to muscle fiber defects with manifestations such as hypotonia. [provided by RefSeq, Sep 2019]

ACMG classification

Verdict is Pathogenic. Variant got 15 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-229432867-C-G is described in Lovd as [Likely_pathogenic].
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), ACTA1. . Gene score misZ 4.5292 (greater than the threshold 3.09). Trascript score misZ 6.088 (greater than threshold 3.09). GenCC has associacion of gene with congenital myopathy with excess of thin filaments, nemaline myopathy 3, intermediate nemaline myopathy, typical nemaline myopathy, congenital fiber-type disproportion myopathy, severe congenital nemaline myopathy, rigid spine syndrome, zebra body myopathy, childhood-onset nemaline myopathy, congenital myopathy 2c, severe infantile, autosomal dominant, alpha-actinopathy, progressive scapulohumeroperoneal distal myopathy.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.923
• PP5: Variant 1-229432868-C-T is Pathogenic according to our data. Variant chr1-229432868-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 196311.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ACTA1	NM_001100.4	c.142G>A	p.Gly48Ser	missense_variant	3/7	ENST00000366684.7	NP_001091.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
ACTA1	ENST00000366684.7	c.142G>A	p.Gly48Ser	missense_variant	3/7	1	NM_001100.4	ENSP00000355645	P1
ACTA1	ENST00000366683.4	c.142G>A	p.Gly48Ser	missense_variant	3/7	5		ENSP00000355644
ACTA1	ENST00000684723.1	c.7G>A	p.Gly3Ser	missense_variant	2/6			ENSP00000508084

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 38

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Aug 19, 2018	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	GeneDx	May 24, 2016	The G48S variant was previously reported as a de novo variant in a patient with congenital myopathy and type I fiber predominance on muscle histology (Witting et al., 2016). It was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The G48S variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved across species, and multiple missense variants at the same and in nearby residues have been reported in the Human Gene Mutation Database in association with ACTA1-related disorders (Stenson et al., 2014), supporting the functional importance of this region of the protein. However, in silico analysis is inconsistent in its predictions as to whether or not the variant is damaging to the protein structure/function. Therefore, this variant is likely pathogenic; however, the possibility that it is benign cannot be excluded. -

Actin accumulation myopathy Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 19, 2022

For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Gly48 amino acid residue in ACTA1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 19562689, 24642510, 25470062). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt ACTA1 protein function. ClinVar contains an entry for this variant (Variation ID: 196311). This missense change has been observed in individual(s) with congenital myopathy (PMID: 26172852; Invitae). In at least one individual the variant was observed to be de novo. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces glycine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 48 of the ACTA1 protein (p.Gly48Ser). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.28	D
BayesDel_noAF	Pathogenic	0.16
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.92	D;D
Eigen	Pathogenic	0.72
Eigen_PC	Uncertain	0.65
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.86	D;T
M_CAP	Uncertain	0.22	D
MetaRNN	Pathogenic	0.92	D;D
MetaSVM	Uncertain	0.74	D
MutationAssessor	Pathogenic	2.9	M;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.93	D
PROVEAN	Uncertain	-3.1	D;N
REVEL	Pathogenic	0.69
Sift	Uncertain	0.0020	.;D
Sift4G	Benign	0.067	T;D
Polyphen		1.0	D;.
Vest4		0.88
MutPred		0.72		Gain of catalytic residue at G48 (P = 0.0196);Gain of catalytic residue at G48 (P = 0.0196);
MVP		0.99
ClinPred		0.99	D
GERP RS		4.7
Varity_R		0.96
gMVP		0.92

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs794727488; hg19: chr1-229568615;